Field of the Invention
The present invention relates to a honeycomb structure, and more particularly, it relates to a honeycomb structure which is for use in exhaust gas purifying device to purify exhaust gas of a gasoline engine and is capable of preventing deterioration of purifying performance of the exhaust gas.
Description of the Related Art
In recent years, for various requests for resource saving, energy saving and the like, there has been advanced development of an engine which suppresses fuel consumption of fossil fuel such as gasoline, further suppresses an amount of exhaust gas to be generated, and exerts low fuel consumption performance. Especially in a gasoline engine which is usually employed as a drive source of a car, for the purpose of satisfying requirements of the above low fuel consumption, there has been advanced a technology concerned with a direct injection type gasoline engine in which the gasoline is directly injected into a cylinder to perform driving.
In the direct injection type gasoline engine, low fuel consumption can be achieved as compared with a conventional “port injection type” gasoline engine. On the other hand, an amount of particulate matter (PM) such as soot to be generated at start of the engine or during acceleration thereof might excessively increase as compared with the conventional gasoline engine. Therefore, the exhaust gas including the generated particulate matter is discharged to the atmosphere through an appropriate treatment.
In the case of a diesel engine, for the purpose of removing the particulate matter in the exhaust gas generated by an operation of the engine, there is attached a trapping filter (exhaust gas purifying device) in which a honeycomb structure is used. As the honeycomb structure for use in the trapping filter, a plugged honeycomb structure is used which includes plugging portions to plug both end faces in accordance with a predetermined arrangement standard (e.g., see Patent Document 1). Consequently, the exhaust gas flows into the plugged honeycomb structure, and passes through partition walls of the plugged honeycomb structure made of a porous ceramic material, whereby the particulate matter is trapped by the partition walls.
Similarly to the above trapping filter for the diesel engine, there is performed development of a trapping filter suitable for the gasoline engine in which the honeycomb structure is used. As a result, it is possible to remove the particulate matter from the exhaust gas and to discharge the purified gas to the atmosphere. Here, when the above trapping filter is attached to the gasoline engine, there is the possibility that pressure loss increases to adversely affect running performance.
Therefore, depending on specifications of a vehicle in which the gasoline engine is mounted, the trapping filter can be designed to slightly decrease trapping efficiency of the particulate matter, thereby suppressing the pressure loss. In this case, it has been suggested to use, as the trapping filter, the honeycomb structure of a one-side plugging structure in which plugging portions are provided only on one end face side of the honeycomb structure in accordance with a predetermined arrangement standard.
[Patent Document 1] JP-A-2003-254034